Strike Puts Spotlight on Teacher Evaluation, Pay

CHICAGO—Teachers in the third-largest U.S. school district went on strike Monday, halting classes for about 350,000 students and casting an election-season spotlight on a growing national debate over how best to evaluate teachers, set their pay and fire them.

Months of acrimonious contract negotiations between the Chicago Teachers Union and Mayor Rahm Emanuel stalled this weekend, apparently over Mr. Emanuel's push to make teacher...